/**
 * Software License, Version 1.0
 * 
 * Copyright 2003 The Trustees of Indiana University.  All rights reserved.
 * 
 *
 *Redistribution and use in source and binary forms, with or without 
 *modification, are permitted provided that the following conditions are met:
 *
 *1) All redistributions of source code must retain the above copyright notice,
 * the list of authors in the original source code, this list of conditions and
 * the disclaimer listed in this license;
 *2) All redistributions in binary form must reproduce the above copyright 
 * notice, this list of conditions and the disclaimer listed in this license in
 * the documentation and/or other materials provided with the distribution;
 *3) Any documentation included with all redistributions must include the 
 * following acknowledgement:
 *
 *"This product includes software developed by the Community Grids Lab. For 
 * further information contact the Community Grids Lab at 
 * http://communitygrids.iu.edu/."
 *
 * Alternatively, this acknowledgement may appear in the software itself, and 
 * wherever such third-party acknowledgments normally appear.
 * 
 *4) The name Indiana University or Community Grids Lab or NaradaBrokering, 
 * shall not be used to endorse or promote products derived from this software 
 * without prior written permission from Indiana University.  For written 
 * permission, please contact the Advanced Research and Technology Institute 
 * ("ARTI") at 351 West 10th Street, Indianapolis, Indiana 46202.
 *5) Products derived from this software may not be called NaradaBrokering, 
 * nor may Indiana University or Community Grids Lab or NaradaBrokering appear
 * in their name, without prior written permission of ARTI.
 * 
 *
 * Indiana University provides no reassurances that the source code provided 
 * does not infringe the patent or any other intellectual property rights of 
 * any other entity.  Indiana University disclaims any liability to any 
 * recipient for claims brought by any other entity based on infringement of 
 * intellectual property rights or otherwise.  
 *
 *LICENSEE UNDERSTANDS THAT SOFTWARE IS PROVIDED "AS IS" FOR WHICH NO 
 *WARRANTIES AS TO CAPABILITIES OR ACCURACY ARE MADE. INDIANA UNIVERSITY GIVES
 *NO WARRANTIES AND MAKES NO REPRESENTATION THAT SOFTWARE IS FREE OF 
 *INFRINGEMENT OF THIRD PARTY PATENT, COPYRIGHT, OR OTHER PROPRIETARY RIGHTS. 
 *INDIANA UNIVERSITY MAKES NO WARRANTIES THAT SOFTWARE IS FREE FROM "BUGS", 
 *"VIRUSES", "TROJAN HORSES", "TRAP DOORS", "WORMS", OR OTHER HARMFUL CODE.  
 *LICENSEE ASSUMES THE ENTIRE RISK AS TO THE PERFORMANCE OF SOFTWARE AND/OR 
 *ASSOCIATED MATERIALS, AND TO THE PERFORMANCE AND VALIDITY OF INFORMATION 
 *GENERATED USING SOFTWARE.
 */

package cgl.narada.util.logging;

import java.lang.reflect.Constructor;
import java.util.Hashtable;


/**
 * 
 * @version 1.0
 * @author Hongbin Liu
 */

public class LoggerFactory {

    private static final 
	String LOG4J_WRAPPER_FQCN = "cgl.narada.util.logging.Log4jLogger";
    private static final 
	String JAVA_WRAPPER_FQCN = "cgl.narada.util.logging.JavaLogger";
    private static final 
	String SIMPLE_LOGGER_FQCN = "cgl.narada.util.logging.SimpleLogger";
    private static final 
	String LOG4J_LOGGER_FQCN = "org.apache.log4j.Logger";
    private static final 
	String JAVA_LOGGER_FQCN = "java.util.logging.Logger";
    
    private static Hashtable instances = new Hashtable();
    private String loggerFQCN;
    private Constructor loggerConstructor = null;
    private Class loggerConstructorSignature[] 
	= { java.lang.String.class };


    /**
     *
     */
    public static Logger getLogger(Class clazz)
        throws LoggingException {

	return (getLogger(clazz.getName()));
    }


    /**
     *
     */
    public static Logger getLogger(String name) 
	throws LoggingException {

        Logger instance = (Logger) instances.get(name);
        if (instance != null) return (instance);

        try {
            Object params[] = new Object[1];
            params[0] = name;
            instance = (Logger) new LoggerFactory().
		getLoggerConstructor().newInstance(params);
	    instances.put(name, instance);
        } catch (Throwable t) {
            throw new LoggingException(t);
        }
        return (instance);

    }

    /**
     *
     */
    public static void release() {

        instances.clear();
    }

    /**
     *
     */
    protected String getLoggerFQCN() {

        if (loggerFQCN != null) {
            return loggerFQCN;
        }

        if ((loggerFQCN == null) && isLog4jAvailable()) {
            loggerFQCN = LOG4J_WRAPPER_FQCN;
        }

        if ((loggerFQCN == null) && isJavaLoggerAvailable()) {
            loggerFQCN = JAVA_WRAPPER_FQCN;
        }

        if (loggerFQCN == null) {
            loggerFQCN = SIMPLE_LOGGER_FQCN;
        }

        return (loggerFQCN);

    }

    /**
     * <p><strong>IMPLEMENTATION NOTE</strong> - Race conditions caused by
     * calling this method from more than one thread are ignored, because
     * the same <code>Constructor</code> instance will ultimately be derived
     * in all circumstances.</p>
     *
     */
    protected Constructor getLoggerConstructor() 
	throws LoggingException {
        
        // Return the previously identified Constructor (if any)
        if (loggerConstructor != null) {
            return loggerConstructor;
        }

        String loggerFQCN = getLoggerFQCN();

        // Attempt to load the Log implementation class
        Class loggerClass = null;
        try {
            loggerClass = Class.forName(loggerFQCN);
            if (loggerClass == null) {
                throw new LoggingException
                    ("No suitable Log implementation for " + loggerFQCN);
            }
            if (!Logger.class.isAssignableFrom(loggerClass)) {
                throw new LoggingException
                    ("Class " + loggerFQCN + " does not implement Logger");
            }
        } catch (Throwable t) {
            throw new LoggingException(t);
        }

        // Identify the corresponding constructor to be used
        try {
            loggerConstructor = loggerClass.getConstructor(loggerConstructorSignature);
            return (loggerConstructor);
        } catch (Throwable t) {
            throw new LoggingException
                ("No suitable Logger constructor " +
                 loggerConstructorSignature+ " for " + loggerFQCN, t);
        }
    }

    /**
     *
     */
    protected boolean isJavaLoggerAvailable() {

        try {
            Class.forName(JAVA_LOGGER_FQCN);
            Class.forName(JAVA_WRAPPER_FQCN);
            return (true);
        } catch (Throwable t) {
            return (false);
        }
    }


    /**
     *
     */
    protected boolean isLog4jAvailable() {

        try {
            Class.forName(LOG4J_LOGGER_FQCN);
            Class.forName(LOG4J_WRAPPER_FQCN);
            return (true);
        } catch (Throwable t) {
            return (false);
        }
    }

}
